[W126 Coupe] Slight miss-fire at idle

[Dick Spellman]

Actually you have two choices.  Buy just the o-rings, replace and see if 
the leak stops.  If the leak stops and the miss goes away, fantastic.  
If the leak stops but, the miss persists, remove the EHA once again and 
remove the flat blade screw on the lower back-side and with tremendous 
care using a 2mm allen hex wrench turn the underlying hex adjustment 
clockwise 90 degrees, replacing the flat head screw when done.  (Careful 
not to exceed the 90 degress and to confirm you have the RIGHT size 
allen wrench, this 2mm adjustment moves verrrry easily)  (Photos on how 
to are available).  This increases the lower chamber fuel distributor 
pressure from approx. .4 bars (factory) to .45 bars and is suggested 
with cars over 100k miles.  If this clears the miss, great.  If the miss 
persists, you need to go through a labyrinth of tests that run from the 
electrics to fuel pressures until you unearth the gremlin.  Been there 
and done that now twice on the in-line 6 300SE's.  Both cured but, not 
just with an eha tweak.  The tweak did improve acceleration performance 
as best I can tell.  I did have a number of other issues to clear and 
any combination could have improved performance where my objective was 
better, no more fuel leak/smell, improved gas mileage and no more miss.  
Maybe one of you will be the first to luck out with just the eha tweak.

If after replacing just the eha o-rings the leak persists you will have 
to replace the entire eha which probably has developed an internal leak.

By the way if you run several MB's that use the eha you may want to 
stock a spare.  The aftermarket supply is dwindling and soon the only 
resource will be the MB stealership with today's price of $414 (this is 
less 20%) and it's rising.  Aftermarket distributor prices were $204 
last Nov and are now $214 as of Feb 1.  Buy one while you can!  Jonathan 
or Rusty should be able to help with these but their prices may have 
already jumped!  I recently heard of $275 as the going price.

Dick

mavris2 at comcast.net wrote:

> "I noticed that I have a fuel leak
> around the o-rings on the altitude box that attaches to the fuel dist,
> would that cause the misfire? Also I have bosch 4 platinum plugs in it,
> should I switch them?
>
> I had the same problem in my sel.  You have to replace the entire 
> E.H.A. Valve
> which comes with new O-ring, and two screws. Its very simply to 
> change. Trust me getting new rings wont solve the problem. When they 
> go bad the leak internaly.  Anyway, I too was runing +4.  Nope they 
> were ok for a couple thousland miles then the slight miss started.  
> Switched back to oem plugs and new EHA and poof miss gone !
>
> Jason
>
> ----- Original Message ----- From: "Pavel" <zhur0002 at umn.edu>
> To: <mbcoupes at mbcoupes.com>
> Sent: Thursday, March 02, 2006 3:33 PM
> Subject: [W126 Coupe] Slight miss-fire at idle
>